Acrylate Ink Compositions For Ink-Based Digital Lithographic Printing

ABSTRACT

Compatible acrylate ink sets include an acrylate ink composition having 30% or less by weight pigment, 10% or less dispersant, between 40% and 80% acrylate, 12% or less photoinitiator, a viscosity between 5×10 5  and 3×10 7  cps at 35° C., and a 60 second tack between 25 and 50 g-m at 35° C.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/645,153, filed Mar. 11, 2015, U. S. Publication NumberUS-2016-0264798-A1, the disclosure of which is totally incorporated byreference herein.

FIELD OF DISCLOSURE

This disclosure relates to ink compositions for printing on substrates.In particular, the disclosure relates to acrylate ink compositionsuseful for digital lithographic printing systems.

BACKGROUND

In typical lithographic printing systems, a printing plate is formed tohave “image regions” formed of a hydrophobic/oleophilic material and“non-image regions” formed of a hydrophilic/oleophobic material. Theimage regions correspond to the areas on the final print (i.e., thetarget substrate) that are occupied by ink, whereas the non-imageregions correspond to the areas on the final print that are not occupiedby said ink. The hydrophilic regions accept and are readily wetted by awater-based fluid, commonly referred to as a dampening fluid or fountainfluid (typically consisting of water and a small amount of alcohol aswell as other additives and/or surfactants to reduce surface tension).The hydrophobic regions repel dampening fluid and accept ink, whereasthe dampening fluid formed over the hydrophilic regions forms a fluid“release layer” for rejecting ink. The hydrophilic regions of theprinting plate thus correspond to unprinted areas, or “non-image areas”,of the final print.

The ink may be transferred directly to a target substrate, such aspaper, or may be applied to an intermediate surface, such as an offset(or blanket) cylinder in an offset printing system.

Typical lithographic and offset printing techniques utilize plates whichare permanently patterned, and are therefore useful only when printing alarge number of copies of the same image (i.e. long print runs), such asmagazines, newspapers, and the like. However, variable data digitallithography or digital offset lithography has been developed as a systemwhich uses a non-patterned reimageable surface that is initiallyuniformly coated with a dampening fluid layer. Regions of the dampeningfluid are removed by exposure to a focused radiation source (e.g., alaser light source) to form pockets. A temporary pattern in thedampening fluid is thereby formed over the non-patterned reimageablesurface. Ink applied thereover is retained in the pockets formed by theremoval of the dampening fluid. The inked surface is then brought intocontact with a substrate, and the ink transfers from the pockets in thedampening fluid layer to the substrate. The dampening fluid may then beremoved, a new uniform layer of dampening fluid applied to thereimageable surface, and the process repeated.

Digital offset lithography printing systems use offset-type inks thatare specifically designed and optimized to be compatible with varioussubsystems, including ink delivery systems and laser imaging systems, toenable high quality digital printing at high speed. Related artoffset-type inks suffer shortfalls including, but not limited to, (1)being difficult to deliver via preferred inking systems, includinganilox roller-type inking systems, (2) being soluble incommonly-employed dampening fluids, such as octamethylcyclotetrasiloxane(D4), (3) causing image background and/or ghosting issues, (4) beingcostly to manufacture and use, and (5) exhibiting inefficient imagetransfer. In addition, when designing multi-color or multi-ink printingsystems, it is important that the ink forming an ink set not only becompatible with the components of the printing system, but also becompatible with the other inks of the ink set. These shortfalls,individually and in combination, tend to narrow a design space withinwhich related art inks are usable in the context of digital offsetlithography printing systems.

SUMMARY

Accordingly, there is a need to develop inks that exhibit improvedqualities and that may address one or all of the above-identifiedshortfalls. Extensive experimentation has revealed that acrylate inkcompositions according to embodiments of this disclosure may provideenhanced ease of delivery to an imaging member, such as a reimageableoffset plate, enhanced transfer efficiency from the reimageable offsetplate, and enhanced print quality on a variety of substrates. Further,these ink compositions do not tend to degrade printing systemcomponents, such as reimageable surfaces of imaging members, with whichthey contact. These acrylate ink compositions should meet varioussub-system requirements imposed by ink-based digital printing systemsthat are configured for variable data lithographic printing. Theserequirements include wettability, releasability from a reimageablesurface of an imaging member, and compatibility with non-aqueousdampening fluids configured for use with ink-based digital printingmethods and systems.

Acrylate ink compositions are provided herein that meet the foregoingrequirements. The disclosed acrylate ink compositions may be effectivelydelivered from an anilox roller-type delivery system to a reimageablesurface of an imaging member during a variable data offset printingoperation in which images on the reimageable surface are changeablebetween cycles of the imaging member. The disclosed acrylate inkcompositions exhibit stable rheology that enables delivery using ananilox roll delivery system, and demonstrate desirable transferabilityto a reimageable surface of an imaging member.

The following presents a simplified summary in order to provide a basicunderstanding of some aspects of one or more embodiments of the presentteachings. This summary is not an extensive overview, nor is it intendedto identify key or critical elements of the present teachings, nor todelineate the scope of the disclosure. Rather, its primary purpose ismerely to present one or more concepts in simplified form as a preludeto the detailed description presented later.

Additional goals and advantages will become more evident in thedescription of the figures, the detailed description of the disclosure,and the claims.

The foregoing and/or other aspects and utilities embodied in the presentdisclosure may be achieved by providing a set of compatible acrylate inkcompositions, including a first acrylate ink composition, comprising afirst pigment; and a second acrylate ink composition, comprising asecond pigment; wherein each of the acrylate ink compositions includes30% or less by weight pigment, based on a total weight of the acrylateink composition, 10% or less by weight dispersant, based on the totalweight of the acrylate ink composition, between 40% and 80% by weightacrylate, based on the total weight of the acrylate ink composition, and12% or less by weight photoinitiator, based on the total weight of theacrylate ink composition, wherein a viscosity of each acrylate inkcomposition is between 5×10⁵ and 3×10⁷ cps at 35° C., and wherein a 60second tack of each acrylate ink composition is between 25 and 50 g-m at35° C.

In another embodiment, each of the acrylate ink compositions furtherincludes 1.5% or less by weight stabilizer, based on the total weight ofthe ink composition; and 12% or less by weight rheology modifier, basedon the total weight of the ink composition.

In another embodiment, each of the acrylate ink compositions includesbetween 10% and 20% pigment; between 2% and 10% dispersant; between 50%and 75% acrylate; 10% or less photoinitiator; 0.4% or less stabilizer;and between 1% and 5% rheology modifier, wherein a viscosity of eachacrylate ink composition is between 8×10⁵ and 2×10⁷ cps at 35° C., andwherein a 60 second tack of each acrylate ink composition is between 35and 45 g-m at 35° C.

In another embodiment, each of the acrylate ink compositions includesbetween 12% and 18% pigment; between 4% and 8% dispersant; between 60%and 70% acrylate; between 5% and 10% photoinitiator; between 0.1% and0.3% stabilizer; and 3% or less rheology modifier, wherein a viscosityof each acrylate ink composition is between 1×10⁶ and 1×10⁷ cps at 35°C., and wherein a 60 second tack of each acrylate ink composition isabout 40 g-m at 35° C.

In another embodiment, the acrylate includes at least one of an acrylatemonomer, acrylate polymer, acrylate oligomer, a trifunctional acrylatemonomer, a polyester acrylate, and mixtures thereof.

In another embodiment, the acrylate includes at least one of a polyesteracrylate oligomer, a tetrafunctional polyester acrylate oligomer, apropoxylated trimethylolpropane triacrylate monomer, an ethoxylatedtrimethylolpropane triacrylate monomer, a higher functionality monomer,and mixtures thereof.

In another embodiment, the photoinitiator is a free-radicalphotoinitiator.

In another embodiment, the first pigment is one of a cyan pigment, amagenta pigment, and a yellow pigment.

In another embodiment, the second pigment is a black pigment.

In another embodiment, the set of ink compositions further includes athird acrylate ink composition, comprising a third pigment; and a fourthacrylate ink composition, comprising a fourth pigment, wherein the firstpigment is a cyan pigment, the second pigment is a magenta pigment, thethird pigment is a yellow pigment, and the fourth pigment is a blackpigment, and wherein the first, second, third, and fourth acrylate inkcompositions are co-miscible with each other.

The foregoing and/or other aspects and utilities embodied in the presentdisclosure may be achieved by providing a method of printing using avariable data digital lithographic printing device, including applying aplurality of acrylate ink compositions to a reimageable surface of animaging member; and transferring the acrylate ink compositions from thereimageable surface to a substrate, wherein each acrylate inkcomposition includes 30% or less by weight pigment, based on a totalweight of the acrylate ink composition, 10% or less by weightdispersant, based on the total weight of the acrylate ink composition,between 40% and 80% by weight acrylate, based on the total weight of theacrylate ink composition, and 12% or less by weight photoinitiator,based on the total weight of the acrylate ink composition, wherein aviscosity of each acrylate ink composition is between 5×10⁵ and 3×10⁷cps at 35° C., and wherein a 60 second tack of each acrylate inkcomposition is between 25 and 50 g-m at 35° C.

In another embodiment, the acrylate ink compositions further include astabilizer and a rheology modifier, and each acrylate ink compositionincludes between 10% and 20% pigment; between 2% and 10% dispersant;between 50% and 75% acrylate; 10% or less photoinitiator; 0.4% or lessby weight stabilizer, based on the total weight of the ink composition;and between 1% and 5% by weight rheology modifier, based on the totalweight of the ink composition; wherein a viscosity of each acrylate inkcomposition is between 8×10⁵ and 2×10⁷ cps at 35° C., and wherein a 60second tack of each acrylate ink composition is between 35 and 45 g-m at35° C.

In another embodiment, each acrylate ink composition includes between12% and 18% pigment; between 4% and 8% dispersant; between 60% and 70%acrylate; between 5% and 10% photoinitiator; between 0.1% and 0.3%stabilizer; and 3% or less rheology modifier, wherein a viscosity ofeach acrylate ink composition is between 1×10⁶ and 1×10⁷ cps at 35° C.,and wherein a 60 second tack of each acrylate ink composition is about40 g-m at 35° C.

In another embodiment, the acrylate includes at least one of an acrylatemonomer, acrylate polymer, acrylate oligomer, a trifunctional acrylatemonomer, a polyester acrylate, and mixtures thereof.

In another embodiment, the acrylate includes at least one of a polyesteracrylate oligomer, a tetrafunctional polyester acrylate oligomer, apropoxylated trimethylolpropane triacrylate monomer, an ethoxylatedtrimethylolpropane triacrylate monomer, a higher functionality monomer,and mixtures thereof.

In another embodiment, the photoinitiator is a free-radicalphotoinitiator.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages in the embodiments of thedisclosure will become apparent and more readily appreciated from thefollowing description of the various embodiments, taken in conjunctionwith the accompanying drawings of which:

FIG. 1 illustrates a variable image digital printing system.

It should be noted that some details of the drawings have beensimplified and are drawn to facilitate understanding of the presentteachings rather than to maintain strict structural accuracy, detail,and scale.

The drawings above are not necessarily to scale, with emphasis insteadgenerally being placed upon illustrating the principles in the presentdisclosure. Further, some features may be exaggerated to show details ofparticular components. These drawings/figures are intended to beexplanatory and not restrictive.

DETAILED DESCRIPTION

Reference will now be made in detail to the various embodiments in thepresent disclosure. The embodiments are described below to provide amore complete understanding of the components, processes and apparatusesdisclosed herein. Any examples given are intended to be illustrative,and not restrictive. Throughout the specification and claims, thefollowing terms take the meanings explicitly associated herein, unlessthe context clearly dictates otherwise. The phrases “in someembodiments” and “in an embodiment” as used herein do not necessarilyrefer to the same embodiment(s), though they may. Furthermore, thephrases “in another embodiment” and “in some other embodiments” as usedherein do not necessarily refer to a different embodiment, although theymay. As described below, various embodiments may be readily combined,without departing from the scope or spirit of the present disclosure.

As used herein, the term “or” is an inclusive operator, and isequivalent to the term “and/or,” unless the context clearly dictatesotherwise. The term “based on” is not exclusive and allows for beingbased on additional factors not described, unless the context clearlydictates otherwise. In the specification, the recitation of “at leastone of A, B, and C,” includes embodiments containing A, B, or C,multiple examples of A, B, or C, or combinations of A/B, A/C, B/C,A/B/B/B/B/C, A/B/C, etc. In addition, throughout the specification, themeaning of “a,” “an,” and “the” include plural references. The meaningof “in” includes “in” and “on.”

All physical properties that are defined hereinafter are measured at 20°to 25° Celsius unless otherwise specified. The term “room temperature”refers to 25° Celsius unless otherwise specified.

When referring to any numerical range of values herein, such ranges areunderstood to include each and every number and/or fraction between thestated range minimum and maximum. For example, a range of 0.5-6% wouldexpressly include all intermediate values of 0.6%, 0.7%, and 0.9%, allthe way up to and including 5.95%, 5.97%, and 5.99%. The same applies toeach other numerical property and/or elemental range set forth herein,unless the context clearly dictates otherwise.

The present disclosure has been described with reference to exemplaryembodiments. Although a few embodiments have been shown and described,it will be appreciated by those skilled in the art that changes may bemade in these embodiments without departing from the principles andspirit of preceding detailed description. It is intended that thepresent disclosure be construed as including all such modifications andalterations insofar as they come within the scope of the appended claimsor the equivalents thereof. For example, while the embodiments below aredescribed in view of the printing system illustrated in FIG. 1, itshould be understood that embodiments of the acrylate ink compositionsdescribed herein may also be used with other compatible printingsystems.

Ink compositions in accordance with embodiments recited herein aresuitable for ink-based digital printing. “Variable data lithographyprinting,” or “ink-based digital printing,” or “digital offsetprinting,” as these terms may be used throughout this disclosure, referto lithographic printing of variable image data for producing images ona substrate that are changeable with each subsequent rendering of animage on the substrate in an image forming process. “Variable datalithographic printing” includes offset printing of ink images usinglithographic ink where the images are based on digital image data thatmay vary from image to image. Ink-based digital printing uses a variabledata lithography printing system or digital offset printing system. A“variable data lithography system” is a system that is configured forlithographic printing using lithographic inks and based on digital imagedata, which may vary from one image to the next.

By way of example, an ink-based digital printing system with anilox rollink delivery subsystem that may be used with embodiments of the acrylateink compositions herein is described in U.S. patent application Ser. No.13/095,714. U.S. patent application Ser. No. 13/095,714 (“714Application”), titled “Variable Data Lithography System,” filed on Apr.27, 2011, by Timothy Stowe et al., which is commonly assigned, and thedisclosure of which is hereby incorporated by reference herein in itsentirety, describes an exemplary variable data lithography system 100for ink-based digital printing in FIG. 1.

A general description of the exemplary printing system 100 shown in FIG.1 is provided below. Additional details regarding individual componentsand/or subsystems shown in the exemplary system 100 of FIG. 1 may befound in the 714 Application.

FIG. 1 illustrates a variable image digital printing system. Asillustrated in FIG. 1, a printing system 100 may include an imagingmember 110. While the imaging member 110 is illustrated in FIG. 1 as adrum, in other embodiments, the imaging member 110 could also beembodied as a plate, belt, or another now known or later developedconfiguration. The imaging member 110 includes a reimageable surfacethat may be formed of materials including, for example, a class ofmaterials commonly referred to as silicones, includingpolydimethylsiloxane (PDMS), among others. For example, silicone,fluorosilicone, and/or fluoroelastomer may be used to form thereimageable surface of the imaging member 110. The reimageable surfacemay be formed of a relatively thin layer over a mounting layer, athickness of the relatively thin layer being selected to balanceprinting or marking performance, durability, and manufacturability.

In some embodiments, the imaging member 110 is used to apply an inkedimage to an image receiving media substrate 114 at a transfer nip 112.The transfer nip 112 may be formed by an impression roller 118, as partof an image transfer mechanism 160, exerting pressure in the directionof the imaging member 110. Image receiving medium substrate 114 shouldnot be considered to be limited to any particular composition, such as;for example, paper, plastic, or composite sheet film. The exemplaryprinting system 100 may be used for producing images on a wide varietyof image receiving media substrates 114. The 714 Application alsoexplains the wide latitude of marking (printing) materials that may beused, including marking materials with pigment densities greater than10% by weight. As does the 714 Application, this disclosure will use theterm ink to refer to a broad range of printing or marking materials toinclude those which are commonly understood to be inks, pigments, andother materials which may be applied by the exemplary system 100 toproduce an output image on the image receiving media substrate 114.

The 714 Application depicts and describes details of the imaging member110 including the imaging member 110 being comprised of a reimageablesurface layer formed over a structural mounting layer that may be, forexample, a cylindrical core, or one or more structural layers over acylindrical core.

The exemplary printing system 100 may include a dampening fluid system120 generally comprising a series of rollers, which may be considered asdampening rollers or collectively as a dampening unit, for uniformlywetting the reimageable surface of the imaging member 110 with dampeningfluid. One purpose of the dampening fluid system 120 is to deliver alayer of dampening fluid, generally having a uniform and controlledthickness, to the reimageable surface of the imaging member 110. Adampening fluid such as fountain solution may comprise mainly wateroptionally with small amounts of isopropyl alcohol or ethanol added toreduce surface tension as well as to lower evaporation energy necessaryto support subsequent laser patterning, as will be described in greaterdetail below. Small amounts of certain surfactants may be added to thefountain solution as well. Alternatively, other suitable dampeningfluids may be used to enhance the performance of ink based digitallithography systems. Extensive experimentation has found that apreferred dampening fluid may be D4 (octamethylcyclotetrasiloxane).Other suitable dampening fluids are disclosed, by way of example, inU.S. patent application Ser. No. 13/284,114, filed on Oct. 28, 2011,titled “Dampening Fluid for Digital Lithographic Printing,” thedisclosure of which is hereby incorporated herein by reference in itsentirety.

Once the dampening fluid is metered onto the reimageable surface of theimaging member 110 by the dampening fluid system 120, a thickness of thedampening fluid may be measured using a sensor 125 that may providefeedback to control the metering of the dampening fluid onto thereimageable surface of the imaging member 110 by the dampening fluidsystem 120.

After an amount of dampening fluid is provided by the dampening fluidsystem 120 on the reimageable surface of the imaging member 110, anoptical patterning subsystem 130 may be used to selectively form alatent image in the uniform dampening fluid layer by image-wisepatterning the dampening fluid layer using, for example, laser energy.Typically, the dampening fluid will not absorb the optical energy (IR orvisible) efficiently. The reimageable surface of the imaging member 110should ideally absorb most of the laser energy (visible or invisiblesuch as IR) emitted from the optical patterning subsystem 130 close tothe surface to minimize energy wasted in heating the dampening fluid andto minimize lateral spreading of heat in order to maintain a highspatial resolution capability. Alternatively, an appropriate radiationsensitive component may be added to the dampening fluid to aid in theabsorption of the incident radiant laser energy. While the opticalpatterning subsystem 130 is described above as being a laser emitter, itshould be understood that a variety of different systems may be used todeliver the optical energy to pattern the dampening fluid.

The mechanics at work in the patterning process undertaken by theoptical patterning subsystem 130 of the exemplary system 100 aredescribed in detail with reference to FIG. 5 in the 714 Application.Briefly, the application of optical patterning energy from the opticalpatterning subsystem 130 results in selective removal of portions of thelayer of dampening fluid.

Following patterning of the dampening fluid layer by the opticalpatterning subsystem 130, the patterned layer over the reimageablesurface of the imaging member 110 is presented to an inker subsystem140. The inker subsystem 140 is used to apply a uniform layer of inkover the layer of dampening fluid and the reimageable surface layer ofthe imaging member 110. The inker subsystem 140 may use an anilox rollerto meter an offset lithographic ink onto one or more ink forming rollersthat are in contact with the reimageable surface layer of the imagingmember 110. Separately, the inker subsystem 140 may include othertraditional elements such as a series of metering rollers to provide aprecise feed rate of ink to the reimageable surface of the imagingmember 110. The inker subsystem 140 may deposit the ink to the pocketsrepresenting the imaged portions of the reimageable surface, while inkon the unformatted portions of the dampening fluid will not adhere tothose portions.

The cohesiveness and viscosity of the ink residing in the reimageablelayer of the imaging member 110 may be modified by a number ofmechanisms. One such mechanism may involve the use of a pre-cure orrheology (complex viscoelastic modulus) control subsystem 150. Therheology control system 150 may form a partial crosslinking core of theink on the reimageable surface to, for example, increase ink cohesivestrength relative to the reimageable surface layer. Curing mechanismsmay include optical or photo curing, heat curing, drying, or variousforms of chemical curing.

The ink is transferred from the reimageable surface of the imagingmember 110 to a substrate of image receiving medium 114 using a transfersubsystem 160. The transfer occurs as the image receiving mediasubstrate 114 is passed through a nip 112 between the imaging member 110and an impression roller 118 such that the ink within the voids of thereimageable surface of the imaging member 110 is brought into physicalcontact with the image receiving media substrate 114. With the adhesionof the ink having been modified by the rheology control system 150,adhesion of the ink may cause the ink to adhere to the image receivingmedia substrate 114 and to separate from the reimageable surface of theimaging member 110. Careful control of the rheology of the ink throughcomposition or other means, as well as temperature and pressureconditions at the transfer nip 112, may allow, or otherwise facilitate,transfer efficiencies for the ink from the reimageable surface of theimaging member 110 to the image receiving media substrate 114 to exceed95%. While it is possible that in some embodiments some dampening fluidmay also wet the image receiving media substrate 114, the volume of sucha dampening fluid will be minimal, and will rapidly evaporate or beabsorbed by the image receiving media substrate 114.

In certain offset lithographic systems, it should be recognized that anoffset roller, not shown in FIG. 1, may first receive the inked imagepattern and then transfer the inked image pattern to a substrateaccording to a known indirect transfer method.

Following the transfer of a high percentage of the ink to the imagereceiving media substrate 114, residual ink and/or residual dampeningfluid should be removed from the reimageable surface of the imagingmember 110, preferably without scraping or wearing the reimageablesurface. For example, an air knife may be employed to remove residualdampening fluid and/or ink. It is anticipated, however, that some amountof ink residue may remain on the reimageable surface. Removal of suchremaining ink residue may be accomplished through use of some form ofcleaning subsystem 170. The 714 Application describes details of such acleaning subsystem 170 including at least a first cleaning member suchas a sticky or tacky member in physical contact with the reimageablesurface of the imaging member 110, the sticky or tacky member removingresidual ink and any remaining small amounts of surfactant compoundsfrom the reimageable surface of the imaging member 110. The sticky ortacky member may then be brought into contact with a smooth roller towhich residual ink may be transferred from the sticky or tacky member,the ink being subsequently stripped from the smooth roller by, forexample, a doctor blade.

The 714 Application details other mechanisms by which cleaning of thereimageable surface of the imaging member 110 may be facilitated.Regardless of the cleaning mechanism, however, in some embodimentscleaning of the residual ink and dampening fluid from the reimageablesurface of the imaging member 110 is needed to preventing ghosting inthe proposed system. Once cleaned, the reimageable surface of theimaging member 110 is again presented to the dampening fluid system 120by which a fresh layer of dampening fluid is supplied to the reimageablesurface of the imaging member 110, and the process is repeated.

The imaging member reimageable surface may preferably be formed of apolymeric elastomer, such as silicone rubber and/or fluorosiliconerubber. The term “silicone” is well understood to those of skill in therelevant art and refers to polyorganosiloxanes having a backbone formedfrom silicon and oxygen atoms and sidechains containing carbon andhydrogen atoms. For the purposes of this application, the term“silicone” should also be understood to exclude siloxanes that containfluorine atoms, while the term “fluorosilicone” is used to cover theclass of siloxanes that contain fluorine atoms. Other atoms may bepresent in the silicone rubber, for example nitrogen atoms in aminegroups which are used to link siloxane chains together duringcrosslinking. The side chains of the polyorganosiloxane can also bealkyl or aryl.

As discussed above, inks that are useful for ink-based digital offsetprinting must possess physical and chemical properties that meet thespecific demands of ink-based digital printing systems such as thesystem shown in FIG. 1. The digital offset ink must be compatible withmaterials with which it is intended to come in contact, including theimaging plate (reimageable surface of the imaging member) and variousdampening fluids, as well as printable substrates such as paper, metal,or plastic. The digital offset ink must also meet all functionalrequirements of the subsystems as imposed by wetting and transferproperties defined by subsystem architecture and materials sets. Inaddition, in some embodiments, each ink in an ink set must be compatiblewith the other inks of the ink set. Compatibility may be defined bypreferred co-miscibility and co-dispersability ranges for the inkswithin an ink set determined in part by the selection of pigments and/orink base used, as well as polarity matching of the ink base components.For example, to minimize phase separation interactions among thepigments and the pigmented inks during transfer of the inks to the imagereceiving media substrate 114, developing inks, such as cyan, magenta,yellow and black inks, in direct proximity with each other, areconfigured to be co-miscible and compatible with each other so as to notphase separate with each other. Similarly, the co-miscibility andcompatibility properties of the inks in an ink set further allowresidual inks on the reimageable surface of the imaging member 110 to beremoved with efficiency by the cleaning subsystem 170.

In some embodiments, inks formulated for ink-based digital printing, ordigital offset inks, are different in many ways from inks developed forother printing applications, including pigmented solvent inks, offsetinks, flexography inks, UV gel inks, and the like. For example, digitaloffset inks contain much higher pigment loading leading to higherviscosities at room temperature than other inks, which can make inkdelivery by way of an anilox roller system difficult. In someembodiments, digital offset inks should not cause the imaging member(reimageable) surface, which may be a silicone, fluorosilicone, orVITON-containing imaging plate or blanket, to swell and should becompatible with dampening fluid options.

Acrylate ink compositions according to the embodiments disclosed hereinhave been found to minimize a solubility of the acrylate inkcompositions in dampening fluid, such as D4, and to minimize or preventswelling of a fluorosilicone-containing imaging member. Acrylate inkcompositions in accordance with embodiments preferably exhibit arheology that is suitable for anilox roller delivery. In addition, someembodiments of the acrylate ink compositions are compatible withnon-aqueous dampening fluids and exhibit desirable releasability fromthe imaging member (reimageable) surface after ink image formation.

According to some embodiments of the present invention, the acrylate inkcomposition is part of an ink set of acrylate ink compositions. In oneembodiment, the acrylate ink compositions within the ink set arecompatible with each other. In some embodiments, each acrylate inkcomposition includes a pigment, an acrylate, a dispersant, and a photoinitiator. In one embodiment, each acrylate ink composition alsoincludes at least one of rheology modifiers, stabilizers, and other inkcomposition additives.

For example, in one embodiment, the acrylate ink compositions mayinclude pigments such as HELIOGEN® Blue D 7088 available from BASF;Permanent Rubine L5B 01 (PR57:1), Permanent Yellow G-MX (PY 14),DHG-CN09 (PY 12), or HOSTAPERM® Blue B4G, available from ClariantCorporation. Other suitable pigments include black pigments, whitepigments, cyan pigments, magenta pigments, yellow pigments, and thelike. Further, pigments may be organic or inorganic particles. Suitableinorganic pigments may include carbon black. However, other inorganicpigments may be suitable such as titanium oxide, and iron oxide.Suitable organic pigments include, for example, azo pigments includingdiazo pigments and monoazo pigments, polycyclic pigments (e.g.,phthalocyanine pigments such as phthalocyanine blues and phthalocyaninegreens), perylene pigments, perinone pigments, anthraquinone pigments,quinacridone pigments, dioxazine pigments, thioindigo pigments,isoindolinone pigments, pyranthrone pigments, and quinophthalonepigments), insoluble dye chelates (e.g., basic dye type chelates andacidic dye type chelate), nitro pigments, nitroso pigments, anthanthronepigments such as PR168, and the like.

Representative examples of phthalocyanine blues and greens includecopper phthalocyanine blue, copper phthalocyanine green, and derivativesthereof (Pigment Blue 15, Pigment Green 7, and Pigment Green 36).Representative examples of quinacridones include Pigment Orange 48,Pigment Orange 49, Pigment Red 122, Pigment Red 192, Pigment Red 202,Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Violet 19,and Pigment Violet 42. Representative examples of anthraquinones includePigment Red 43, Pigment Red 194, Pigment Red 177, Pigment Red 216 andPigment Red 226. Representative examples of perylenes include PigmentRed 123, Pigment Red 149, Pigment Red 179, Pigment Red 190, Pigment Red189 and Pigment Red 224. Representative examples of thioindigoidsinclude Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181,Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.Representative examples of heterocyclic yellows include Pigment Yellow1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, PigmentYellow 14, Pigment Yellow 17, Pigment Yellow 65, Pigment Yellow 73,Pigment Yellow 74, Pigment Yellow 90, Pigment Yellow 110, Pigment Yellow117, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 138, PigmentYellow 150, Pigment Yellow 151, Pigment Yellow 155, Pigment Yellow 180and Pigment Yellow 213. Such pigments are commercially available ineither powder or press cake form from a number of sources including,BASF Corporation, Engelhard Corporation, and Sun Chemical Corporation.

Examples of black pigments that may be used include carbon pigments. Thecarbon pigments may be almost any commercially available carbon pigmentthat provides acceptable optical density and print characteristics.Carbon pigments suitable for use in systems and methods in accordancewith embodiments may include, without limitation, carbon black,graphite, vitreous carbon, charcoal, and combinations thereof. Suchcarbon pigments can be manufactured by a variety of known methods, suchas a channel method, a contact method, a furnace method, an acetylenemethod, or a thermal method, and are commercially available from suchvendors as Cabot Corporation, Columbian Chemicals Company, Evonik, OrionEngineered Carbons, and E.I. DuPont de Nemours and Company. Suitablecarbon black pigments include, without limitation, Nipex® 150 or Nipex®35 (available from Orion Engineered Carbons), Cabot pigments such asMONARCH® 1400, MONARCH® 1300, MONARCH® 1100, MONARCH® 1000, MONARCH®900, MONARCH® 880, MONARCH® 800, MONARCH® 700, CAB-O-JET® 200,CAB-O-JET® 300, REGAL®, BLACK PEARLS®, ELFTEX®, MOGUL® E, MOGUL® L, andVULCAN® pigments; Columbian pigments such as RAVEN® 5000, and RAVEN®3500; Evonik pigments such as Color Black FW 200, FW 2, FW 2V, FW 1,FW18, FW S160, FW S170, Special Black 6, Special Black 5, Special Black4A, Special Black 4, PRINTEX® U, PRINTEX® 140U, PRINTEX® V, and PRINTEX®140V. The above list of pigments includes unmodified pigmentparticulates, small molecule attached pigment particulates, andpolymer-dispersed pigment particulates. Other pigments can also beselected, as well as mixtures thereof. In some embodiments, the pigmentparticle size is desired to be as small as possible to enable a stablecolloidal suspension of the particles in the liquid vehicle, forexample.

In one embodiment, the acrylate ink composition includes 30% or lesspigment by weight, based on a total weight of the acrylate inkcomposition. In another embodiment, the acrylate ink compositionincludes 20% or less pigment. In another example, the acrylate inkcomposition includes between 10% and 20% pigment. In yet anotherexample, the acrylate ink composition includes between 12% and 18%pigment. In another example, the acrylate ink composition includes 15%or 17.5% pigment.

In some embodiments, the acrylate ink compositions may include anacrylate. Acrylates or propenoates are salts and esters of acrylic acid.Acrylate and methacrylate monomers are understood to contain reactivevinyl functional groups that facilitate formation of acrylate polymers.Exemplary acrylates may include acrylate monomers, oligomers, orpolymers, such as, difunctional monomers, for example, Sartomer SR247,Sartomer CD595 and Sartomer SR9003, trifunctional monomers, for example,Sartomer SR492, Sartomer SR9020, Sartomer SR501, Sartomer SR454 andSartomer SR9035, and polyester acrylates, for example, Sartomer CN294E,Sartomer CN2282, Sartomer CN2295, Sartomer CN2264, Sartomer CN2256, andfrom Allnex, EBECRYL® 450, EBECRYL® 657 and EBECRYL® 809. In oneembodiment, the acrylate ink composition includes at least one of apolyester acrylate oligomer, such as a tetrafunctional polyesteracrylate oligomer; a propoxylated trimethylolpropane triacrylatemonomer; ethoxylated trimethylolpropane triacrylate monomer, andmixtures thereof. In one embodiment, the acrylate ink compositionincludes compatible higher functionality monomers (n-4, 5, 6, etc.).

In one embodiment, the acrylate ink composition includes between 40% and80% acrylate by weight, based on a total weight of the acrylate inkcomposition. In another embodiment, the acrylate ink compositionincludes between 50% and 75% by weight acrylate. In yet another example,the acrylate ink composition includes between 60% and 70% by weightacrylate. In one example, the acrylate ink composition includes between65% and 70% acrylate.

In some embodiments, the acrylate ink compositions may include adispersant. The dispersants may include polymeric dispersants, such asthose from Lubrizol including SOLSPERSE™ 32000, SOLSPERSE™ 39000,SOLSPERSE™ 71000, SOLSPERSE™ J-100, SOLSPERSE™ J-180, SOLSPERSE™ J-200,SOLSPERSE™ X300, and from BASF, such as EFKA® 4300, EFKA® 4330, EFKA®4340, EFKA® 4400, EFKA® PX 4701, EFKA® 4585, EFKA® 5207, EFKA® 6230,EFKA® 7701, EFKA® 7731, and from Tego®, such as TEGO® Dispers 656, TEGO®Dispers 685, TEGO® Dispers 710, and from King Industries, such asK-SPERSE® A-504.

In one embodiment, the acrylate ink composition includes 10% or lessdispersant by weight, based on a total weight of the acrylate inkcomposition. In another example, the acrylate ink composition includesbetween 2% and 10% dispersant. In yet another example, the acrylate inkcomposition includes between 4% and 8% dispersant.

In some embodiments, the acrylate ink compositions may include rheologymodifiers. Exemplary rheology modifiers may be modified or unmodifiedinorganic compounds including organoclays, attapulgite clays andbentonite clays, including tetraallkyl ammonium bentonites as well astreated and untreated synthetic silicas. Suitable organoclays includefrom Southern Clay Products CLAYTONE® HA and CLAYTONE® HY. Suitableexamples of tetraallkyl ammonium bentonites include from CeleritasChemicals CELCHEM 31743-09, CELCHEM 31744-09, and CELCHEM 31745-09.Other exemplary rheology modifiers include organic compounds such asEFKA® RM1900 and EFKA® RM1920, both modified hydrogenated castor oilsfrom BASF.

In one embodiment, the acrylate ink composition includes 12% or lessrheology modifiers by weight, based on a total weight of the acrylateink composition. In another example, the acrylate ink compositionincludes between 1% and 5% rheology modifiers. In yet another example,the acrylate ink composition includes 3% or less rheology modifiers. Inone embodiment, the acrylate ink composition includes 2% rheologymodifiers.

In some embodiments, the acrylate ink compositions may includephotoinitiators. Photoinitiators may be liquid- or solid-based orcombinations thereof. Suitable Type I photoinitiators include those fromclasses of dialkoxy-aceto-pheonones, dialkoxy-alkyl-pheonones,amino-alkyl-pheonones, and acyl-phosphine oxides. Suitable Type IIphotoinitiators include those from classes of benzophenones andthioxanthones, which require activation from suitable amine synergists.Exemplary photoinitiators include ADDITOL® LX, ADDITOL® DX, ADDITOL®BDK, ADDITOL® CPK, ADDITOL® DMMTA, ADDITOL® TPO from Allnex, Esacure®1001M, IRGACURE® 127, IRGACURE® 184, IRGACURE® 379, IRGACURE® 819 andIRGACURE® 2959 from BASF. Exemplary amine synergists that are used withType II photoinitiators include SPEEDCURE PDA, SPEEDCURE EDB fromLambson, Diethylaminoethyl Methacrylate, Ethyl-4-dimethylamino benzoate,2-Ethylhexyl 4-dimethylamino benzoate from Esstech, Inc. In someembodiment, the acrylate ink composition may include low odorphotoinitiators, such as, ESACURE® KIP 150 available from LambertiS.p.A. In other embodiments, the acrylate ink composition may includefree radical photoinitiators in single or mixed systems.

In one embodiment, the acrylate ink composition includes 12% or lessphotoinitiators by weight, based on a total weight of the acrylate inkcomposition. In another example, the acrylate ink composition includes10% or less photoinitiators. In yet another example, the acrylate inkcomposition includes between 5% and 10% photoinitiators. In oneembodiment, the acrylate ink composition includes between 6% and 8% byweight photoinitiators.

In some embodiments, the acrylate ink compositions may includestabilizer polymerization inhibitors or stabilizers. For example, thestabilizers may include Sartomer USA CN3216 (an active componentproprietary stabilizer with p-methoxyphenol in a proprietary acrylatemonomer and a proprietary acrylate oligomer), BASF IRGASTAB® UV22 (ahindered phenol), and GENORAD® 16 and GENORAD® 18, both from Rahn USACorporation.

In one embodiment, the acrylate ink composition includes 1.5% or lessactive component stabilizers by weight, based on a total weight of theacrylate ink composition. In another example, the acrylate inkcomposition includes 0.4% or less stabilizers. In another example, theacrylate ink composition includes between 0.1% and 0.3% stabilizers. Inone embodiment, the acrylate ink composition includes 0.2% stabilizers.

Acrylate ink compositions in accordance with the embodiments describedherein may be formed by preparing an ink base and mixing it with one ormore of the components recited above.

Aspects of the present disclosure may be further understood by referringto the following examples. The examples are illustrative, and are notintended to be limiting embodiments thereof. The examples belowillustrate embodiments of acrylate ink compositions using cyan, magenta,yellow, and black pigments.

Example C1

Based on a total 400 gram scale of preparation for a cyan inkcomposition, 4.5% wt. of SOLSPERSE® 39000, 50.53% wt. of CN294E, 9.1% ofCN2256, 11.65% of SR-9035, and 11% wt. of CN3216 were added to a 1 literstainless steel vessel and placed on a heating mantle (available fromIKA®) together with a thermocouple and stirrer apparatus (also availablefrom IKA®) and equipped with an anchor impeller. The components in thevessel (dispersant, acrylates, and stabilizer) were then stirred at 200RPM for 30 minutes at 80° C. Thereafter photoinitiators (2% wt. Irgacure379, 1.39% wt. Irgacure® 819, and 3.62% wt. Esacure® Kip 150) were addedslowly to the vessel and stirred at about 80° C. for another hour. Withthe components in the vessel solubilized, 15% wt. of Heliogen® Blue D7088 pigment was added to the vessel and stirred more vigorously but notthe point where air was entrained into the mixture. The pigmentedmixture was allowed to stir for about 30 minutes at about 400 RPM atwhich point 2% wt. Claytone® HY was added slowly to the pigmentedmixture at a reduced RPM and then re-stirred for about another 15minutes at about 400 RPM. The vessel containing the mixed components wastransferred to a high speed shearing mill available from the HockmeyerEquipment Corporation equipped with a 40 mm diameter high shear Cowlesblade which was then stirred at 5300 RPM for about an hour. Thethoroughly mixed component mixture was then qualitatively transferred toa 3-roll mill apparatus manufactured by Kent Machine Works where thematerial composite paste was passed through the 3-roll mill first at aninput apron roll speed of 400 RPM for the first pass and then at aninput apron roll speed of 200 RPM for the second pass. The vesselcontaining the mixed components was then transferred to a high speedshearing mill (available from the Hockmeyer Equipment Corporation)equipped with a 40 mm diameter high shear Cowles blade and stirred at5300 RPM for about an hour. The thoroughly mixed component mixture wasthen qualitatively transferred to a 3-roll mill apparatus (manufacturedby Kent Machine Works) where it was passed through the 3-roll mill firstat an input apron roll speed of 400 RPM for a first pass and then at aninput apron roll speed of 200 RPM for a second pass to form Example C1cyan acrylate ink composition. The component percentages of Example C1are summarized in Table 1 below.

Examples C2, C3, C4, and C5

Additional examples of cyan acrylate ink compositions were prepared inthe same manner as Example C1 using cyan pigments and the componentspercentages detailed in Table 1.

TABLE 1 Formulation of Example Inks C1, C2, C3, C4, and C5 InkComposition Formulation Available Component from C1 C2 C3 C4 C5 PigmentHELIGOEN ® BASF 15 15 17.5 — — Blue D 7088 HOSTAPERM ® Clariant — — — 1517.5 Blue B4G Corp. Dispersant Solsperse ® Lubrizol 4.5 4.5 5.25 4.5 739000 Corp. Oligomer CN294E Sartomer Co. 50.53 65 62 65 61.73 CN2256Sartomer Co. 9.1 — — — — Monomer SR-501 Sartomer Co. — 5.49 — 5.49 1.76SR-9035 Sartomer Co. 11.65 — 5.24 — — Photoinitiator Irgacure ® 379 BASF2 2 2 2 2 Irgacure ® 819 BASF 1.39 1.39 1.39 1.39 1.39 Esacure ® KIPLamberti 3.62 3.62 3.62 3.62 3.62 150 Technologies Stabilizer CN3216Sartomer Co. — 1 1 1 1 IRGASTAB ® BASF 0.2 — — — — UV-10 RheologyClaytone ® HY Southern 2 2 2 2 4 Modifier Clay Products Total WeightPercentage 100 100 100 100 100

As illustrated in Table 1, different cyan acrylate ink compositions wereobtained. These acrylate ink compositions had favorable pigment wettingand dispersion characteristics, and remained stable over many monthswithout showing signs of syneresis.

Examples M1, M2, M3

Magenta acrylate ink compositions were prepared in the same manner asExample C1 using magenta pigments and the components percentagesdetailed in Table 2.

TABLE 2 Formulation of Example Inks M1, M2, and M3 Ink CompositionFormulation Component Available From M1 M2 M3 Pigment Permanent Clariant15 15 15 Rubine L5B Corp. 01 (PR57:1) Dispersant Solsperse ® Lubrizol 6— — 39000 Corp. Solsperse ® Lubrizol — 6 4.5 J-180 Corp. Oligomer CN294ESartomer Co. 55.72 48.91 65 CN2256 Sartomer Co. — 8.81 — Monomer SR-501Sartomer Co. 11.27 11.27 5.49 Photo- Irgacure ® BASF 2 2 2 initiator 379Irgacure ® BASF 1.39 1.39 1.39 819 Esacure ® Lamberti 3.62 3.62 3.62 KIP150 Technologies Stabilizer CN3216 Sartomer Co. 1 1 1 RheologyClaytone ® Southern Clay 4 2 2 Modifier HY Products Total WeightPercentage 100 100 100

As illustrated in Table 2, different magenta acrylate ink compositionswere obtained using substantially similar and compatible components asthose in Examples C1-C5. These acrylate ink compositions had favorablepigment wetting and dispersion characteristics, and remained stable overmany months without showing signs of syneresis.

Examples Y1, Y2, and Y3

Yellow acrylate ink compositions were prepared in the same manner asExample C1 using yellow pigments and the components percentages detailedin Table 3.

TABLE 3 Formulation of Example Inks Y1, Y2, and Y3 Ink CompositionFormulation Component Available From Y1 Y2 Y3 Pigment Permanent Clariant17.5 — — Yellow Corp. DHG-CN09 (PY 12) Permanent Clariant — 17.5 17.5Yellow G- Corp. MX (PY 12) Dispersant Solsperse ® Lubrizol 4.8 4.8 4.839000 Corp. Oligomer CN294E Sartomer Co. 61.89 61.89 57.39 CN2256Sartomer Co. — — 4.5 Monomer SR-501 Sartomer Co. 5.8 5.8 5.8 Photo-Irgacure ® BASF 2 2 2 initiator 379 Irgacure ® BASF 1.39 1.39 1.39 819Esacure ® Lamberti 3.62 3.62 3.62 KIP 150 Technologies Stabilizer CN3216Sartomer Co. 1 1 1 Rheology Claytone ® Southern Clay 4 2 2 Modifier HYProducts Total Weight Percentage 100 100 100

As illustrated in Table 3, different yellow acrylate ink compositionswere obtained using substantially similar and compatible components asthose in Examples C1-C5 and M1-M3 above. These acrylate ink compositionshad favorable pigment wetting and dispersion characteristics, andremained stable over many months without showing signs of syneresis.

Examples K1, K2, K3, K4, and K5

Black acrylate ink compositions were prepared in the same manner asExample C1 using black pigments and the components percentages detailedin Table 4.

TABLE 4 Formulation of Example Inks K1, K2, K3, K4, and K5 InkComposition Formulation Available Component from K1 K2 K3 K4 K5 PigmentNIPEX ® 150 Orion 17.5 17.5 — — — Engineered Carbons MOGUL ® E CabotCorp. — — 17.5 — — NIPEX ® 35 Orion — — — 17.5 17.5 Engineered CarbonsDispersant Solsperse ® Lubrizol — — — — 5.25 39000 Corp. Solsperse ®Lubrizol 5.25 — — — — 71000 Corp. Solsperse ® Lubrizol — 5.25 5.25 5.25— J-200 Corp. Oligomer CN294E Sartomer Co. 62 62 62 62 62 Monomer SR-501Sartomer Co. 5.24 5.24 5.24 5.24 5.24 Photoinitiator Irgacure ® 379 BASF2 2 2 2 2 Irgacure ® 819 BASF 1.39 1.39 1.39 1.39 1.39 Esacure ® KIPLamberti 3.62 3.62 3.62 3.62 3.62 150 Technologies Stabilizer CN3216Sartomer Co. 1 1 1 1 1 Rheology Claytone ® HY Southern 2 2 2 2 2Modifier Clay Products Total Weight Percentage 100 100 100 100 100

As illustrated in Table 4, different black acrylate ink compositionswere obtained using substantially similar and compatible components asthose in the examples above. These acrylate ink compositions hadfavorable pigment wetting and dispersion characteristics, and remainedstable over many months without showing signs of syneresis.

The example acrylate ink compositions above were analyzed in terms ofrheology and tack. In particular, the frequency-based sweep rheologies,between applied 0.1 and 100 rad/s frequencies, of all inks weredetermined on a RFS-3 rheometer (available from TA Instruments) at 35°C. equipped with a 25 mm plate at a 0.5 mm gap.

Accordingly, in some embodiments, the acrylate ink composition has anear-zero shear viscosity of between 5×10⁵ and 3×10⁷ cps at 35° C. Inother embodiments, the acrylate ink composition has near-zero shearviscosity of between 8×10⁵ and 2×10⁷ cps at 35° C. In yet anotherembodiment, the acrylate ink composition has near-zero shear viscosityof between 1×10⁶ and 1×10⁷ cps at 35° C.

Similarly, each of the acrylate ink compositions in the examples abovewas tested on an Inkometer 1100 (available from Thwing-Albert Company)to determine tack. The UV ink-rated rollers on the Inkometer wereequilibrated at 32.2° C. In each case, 1.3 mL of the ink composition wasapplied to the distribution roller where transfer and distribution on tothe other rollers was allowed to continue for 15 seconds at 150 RPM uponwhich time the speed of the rollers was automatically increased to 1200RPM. Tack measurements of the ink occurred every 20 seconds for 10minutes. Tack was measured in terms of grams-meters.

In some embodiments, the acrylate ink compositions have a tackmeasurement of between 25 g-m and 50 g-m at 60 seconds and 35° C. Inanother embodiment, the acrylate ink compositions have a tackmeasurement of between 35 and 45 g-m at 60 seconds and 35° C. In oneembodiment, the acrylate ink composition has a tack measurement of 40g-m at 60 seconds and 35° C.

In some embodiments, the acrylate ink composition has a mid-rangeviscosity at 35° C., allowing for anilox delivery. In one embodiment,the acrylate ink composition has a high tack of about 30 and 50 g-m at35° C., enabling efficient transfer to the printing substrate and goodimage quality.

In some embodiments, acrylate ink compositions with a higher tack arebeneficial for increased ink transfer and image quality when used inprinting systems, such as digital lithographic printing systems.

In some embodiments, acrylate ink compositions in accordance with theembodiments of this disclosure are compatible with dampening fluids andimaging member or reimageable surface/plate materials of ink-baseddigital printing systems. For example, embodiments of the acrylate inkcompositions may be immiscible in dampening fluids, such as D4, andprovide low background in non-imaging areas.

In other embodiments, ink sets are formed of acrylate ink compositionshaving substantially similar components. In some embodiments, ink setsformed of acrylate ink compositions are mutually compatible. In otherembodiments, acrylate ink compositions using similar and compatiblecomponents have similar wet-on, curing robustness, and color qualitycharacteristics. In some embodiments, the characteristics of acrylic inkcompositions in an ink set are similar not only among inks of the samecolor, but amount all colors in the ink set. In one embodiment, acrylicink compositions within an ink set are processed in a similar manner inthe printing system.

In order to determine the compatibility of ink sets includingembodiments of acrylate ink compositions in this disclosure, thecoloristic properties of the Example inks above were obtained asfollows.

Some of the Example inks above (C2, M3, Y1, K2, K3 and K4) were imagedon paper in the following manner Each of the inks were applied onto arepresentative portion of the reimageable surface of the imaging member110 with a Brayer roller of Durometer 60 hardness and immediatelytransferred onto XEROX® Digital Color Elite Gloss® (DCEG) paper with aclean Brayer roller of Durometer 60 hardness at different densities suchthat the resultant optical densities of the cyan, magenta, yellow, andblack images were between 1.5 and 1.8, respectively, after having beencured using a Fusion UV Lighthammer® L6 300 W/inch curing stationequipped with D bulb. The applied energy doses for UVV, UVA, UVB, andUVC bands were 640, 1401, 420, and 37 mJ/cm², respectively. The printimage dimensions were about 2 cm by 3 cm.

A spectrodensitometer (X-Rite 538, available from X-Rite) was used tomeasure the color properties of all of the printed ink images using D50and 2° settings. Each of the images was measured 3 times with the meandata reported in Table 6 below in terms of their CIE 1976 color space orCIELAB color space.

TABLE 6 Coloristic Data for CMYK Example Inks Tack at 32.2° C., PigmentComplex Viscosity g-m Grade and (35° C.) @ Frequency, 60 C.I. ColoristicData mPa · s second Example Number O.D. L* a* b* 0.1 rad/s 100 rad/stack C2 HELIOGEN ® 1.50 54.36 34.26 −52.16 3.40E+06 1.05E+05 35.5 Blue D7088, C.I. PB15:3 M3 Permanent 1.52 44.91 71.07 −8.59 8.49E+04 4.87E+0446.8 Rubine L5B 01, C.I. PR57:1 Y1 Permanent 1.51 90.36 −3.10 105.105.35E+05 5.36E+04 41.4 Yellow DHG-CN09, C.I. PY12 K2 Nipex ® 1.79 12.992.13 3.36 8.24E+06 2.01E+05 n/a 150, C.I. P.Bl. 7 K3 Mogul ® E, 1.8012.02 1.33 2.27 6.58E+04 3.85E+04 34.5 C.I. P.Bl. 7 K4 Nipex ® 35, 1.8511.97 0.82 1.03 8.41E+06 1.12E+05 n/a C.I. P.Bl. 7

As illustrated in Table 6, the L* a* b* coloristic data of the CMYacrylate ink compositions corresponded to their respective opticaldensities near 1.5. This data indicated excellent color development. TheL* a* b* data of K acrylic ink compositions at a visible optical densitynear 1.8 and based on three different C.I. Pigment Black 7 grades, alsoshowed an appropriate L* and the preferred near-neutral colorcharacteristics. Accordingly, in one embodiment, acrylate inkcompositions in a variety of colors and/or black pigments can berealized which are compatible and use substantially similar componentswhile delivering desirable coloristic characteristics.

The present disclosure has been described with reference to exemplaryembodiments. Although a few embodiments have been shown and described,it will be appreciated by those skilled in the art that changes may bemade in these embodiments without departing from the principles andspirit of preceding detailed description. It is intended that thepresent disclosure be construed as including all such modifications andalterations insofar as they come within the scope of the appended claimsor the equivalents thereof.

1. An acrylate ink composition comprising: a tetrafunctional polyesteracrylate oligomer; a polyester acrylate oligomer that is different thanthe tetrafunctional polyester acrylate oligomer; a pigment; an optionaldispersant; and an optional photoinitiator.
 2. The ink composition ofclaim 1, further comprising: at least one member of the group consistingof a propoxylated trimethololpropane triacrylate monomer and anethoxylated trimethylolpropane triacrylate monomer.
 3. The inkcomposition of claim 1, further comprising: at least one member of thegroup consisting of a propoxylated trimethololpropane triacrylatemonomer, an ethoxylated trimethylolpropane triacrylate monomer, and amonomer having a functionality greater than or equal to
 4. 4. The inkcomposition of claim 1, wherein a viscosity of the ink composition isbetween 5×10⁵ and 3×10⁷ cps at 35° C.
 5. The ink composition of claim 1,wherein a 60 second tack of the ink composition is between 25 and 50 g-mat 35° C.
 6. The ink composition of claim 1, wherein the ink compositioncomprises between 40% and 50% by weight acrylate, based on a totalweight of the ink composition; 30% or less by weight pigment, based onthe total weight of the ink composition; 10% or less by weightdispersant, based on the total weight of the ink composition; and 12% orless by weight photoinitiator, based on the total weight of the inkcomposition.
 7. The ink composition of claim 1, further comprising: astabilizer; and a rheology modifier; wherein the ink compositioncomprises: between 10% and 20% pigment; between 2% and 10% dispersant;between 40% and 50% acrylate; 10% or less photoinitiator; 0.4% or lessstabilizer; between 1% and 5% rheology modifier; wherein a viscosity ofthe ink composition is between 8×10⁵ and 2×10⁷ cps at 35° C.; andwherein a 60 second tack of the ink composition is between 35 and 45 g-mat 35° C.
 8. The ink composition of claim 1, further comprising: astabilizer; and a rheology modifier; wherein the ink compositioncomprises: between 12% and 18% pigment; between 4% and 8% dispersant;between 40% and 50% acrylate; between 5% and 10% less photoinitiator;between 0.1% and 0.3% stabilizer; 3% or less rheology modifier; whereina viscosity of the ink composition is between 1×10⁶ and 1×10⁷ cps at 35°C.; and wherein a 60 second tack of the ink composition is about 40 g-mat 35° C.
 9. The ink composition of claim 1, wherein the photoinitiatoris a free-radical photoinitiator.
 10. The ink composition of claim 1,wherein the pigment is one of a cyan pigment, a magenta pigment, ayellow pigment, or a black pigment.
 11. A set of compatible acrylate inkcompositions comprising: a first acrylate ink composition comprising afirst pigment; a second acrylate ink composition comprising a secondpigment; wherein each of the acrylate ink compositions comprises: atetrafunctional polyester acrylate oligomer; a polyester acrylateoligomer that is different than the tetrafunctional polyester acrylateoligomer; an optional dispersant; and an optional photoinitiator. 12.The set of compatible acrylate ink compositions of claim 11, whereineach of acrylate ink compositions further comprises: at least one memberof the group consisting of a propoxylated trimethololpropane triacrylatemonomer and an ethoxylated trimethylolpropane triacrylate monomer. 13.The set of compatible acrylate ink compositions of claim 11, whereineach of acrylate ink compositions further comprises: at least one memberof the group consisting of a propoxylated trimethololpropane triacrylatemonomer, an ethoxylated trimethylolpropane triacrylate monomer, and amonomer having a functionality greater than or equal to
 4. 14. The setof compatible acrylate ink compositions of claim 11, wherein a viscosityof each of the ink compositions is between 5×10⁵ and 3×10⁷ cps at 35° C.15. The set of compatible acrylate ink compositions of claim 11, whereina 60 second tack of each of the ink composition is between 25 and 50 g-mat 35° C.
 16. The set of compatible acrylate ink compositions of claim11, wherein each of the ink compositions comprises: between 40% and 50%by weight acrylate, based on a total weight of the ink composition; 30%or less by weight pigment, based on the total weight of the inkcomposition; 10% or less by weight dispersant, based on the total weightof the ink composition; and 12% or less by weight photoinitiator, basedon the total weight of the ink composition.
 17. The set of compatibleacrylate ink compositions of claim 11, wherein each of the inkcompositions further comprises: a stabilizer; and a rheology modifier.18. The set of compatible acrylate ink compositions of claim 11, whereineach of the ink compositions further comprises: a rheology modifier; andwherein each of the ink compositions comprises: between 12% and 18%pigment; between 4% and 8% dispersant; between 40% and 50% acrylate;between 5% and 10% less photoinitiator; between 0.1% and 0.3%stabilizer; 3% or less rheology modifier; wherein a viscosity of eachink composition is between 1×10⁶ and 1×10⁷ cps at 35° C.; and wherein a60 second tack of each ink composition is about 40 g-m at 35° C.
 19. Theset of compatible acrylate ink compositions of claim 11, wherein thephotoinitiator is a free-radical photoinitiator.
 20. The set ofcompatible acrylate ink compositions of claim 11, wherein the firstpigment is one of a cyan pigment, a magenta pigment, and a yellowpigment; and wherein the second pigment is a black pigment.